Conventional electrical plugs are undesirable because they typically include a housing which protrudes a substantial distance from the wall once the plug is inserted into the outlet. This protrusion makes the plug susceptible to unintentional disengagement by moving objects and also prevents furniture and other objects from being placed close to the wall.
Over the years a variety of plugs have been developed which have low profile housings (hereinafter referred to as "low profile plugs"). Low profile plugs are advantageous because they have a reduced housing profile in comparison to conventional electrical plugs. As such, they are less susceptible to unintentional disengagement and permit objects to be placed closer to the wall than is possible with conventional plugs.
In most low profile plugs, the power cord exits the plug perpendicular to the prongs so as to decrease the profile of plug's housing. Hence, when the plug is inserted into a wall outlet, the power cord exits the plug housing parallel to the face of the wall outlet. These plugs are undesirable because it is possible for the cord to block other receptacles in the outlet, thereby preventing additional plugs from being inserted into the outlet. This is even more of a problem with polarized plugs or plugs incorporating a ground prong since these plugs can only be inserted into the wall outlet in one orientation.
In recognition of this problem, it is known to orient the electrical cord to ensure that it does not overlay the other receptacles in the outlet. Examples of such designs are illustrated in U.S. Pat. Nos. 4,927,376 issued to Dickie and 3,975,075 issued to Mason. Dickie discloses a low profile plug in which the cord exits the plug body at an acute angle with respect to a vertical axis of the plug. The cord then passes through a sleeve that reorients the cord with the vertical axis. Similarly, Mason discloses a profile plug in which the cord exits tangentially from a circular plug housing at such an angle that it does not overlay the other receptacles in a standard wall outlet. When several plugs are inserted into a single wall outlet, such plug designs are undesirable because all of the cords leave the outlet in the same direction. As such it is difficult to route electrical cords in several directions from a single wall outlet without entangling the various cords. Besides being unsightly, tangled electrical cords should be avoided because they can be dangerous.
This problem can be addressed by a plug design in which the cord rotates with respect to the prongs. In addition to addressing the above problems, a rotatable plug allows the electrical device connected to the plug to be moved relative to the outlet without imparting excessive forces on the prongs of the plug.
Numerous designs for rotatable plugs have been proposed in the past. In one known design, annular conductors are used to interconnect the power cord with the electrical prongs. Some plugs of this design do not provide for more than two electrical prongs. As a result, these plugs are not suitable for devices requiring a grounding prong. Moreover, plugs of this design are difficult and costly to manufacture and they often fail to meet applicable safety standards, such as those established by the United Laboratories (hereinafter "UL").
An alternative to the above design is to directly connect the power cord conductors to the prongs. This latter design is not acceptable, however, because it can impose excessive bending forces on the power cord conductors. As a result, plugs of this design may have an undesirably short operating life and may also fail to meet applicable safety standards.
Accordingly, an object of the present invention is to provide an electrical plug in which the power cord is rotatable relative to the prongs carried by the plug's housing.
Another object of the present invention to provide a rotatable plug which meets the applicable UL standards.
A further object of the present invention is to provide a rotatable electrical plug which has a reduced housing profile when compared to conventional electrical plugs.
Still a further object of the present invention is to provide an electrical plug and power cord combination in which the power cord can be rotated relative to the plug's prongs without imparting forces on the power cord conductors.
Another object of the present invention to provide a rotatable electrical plug which can incorporate two electrical prongs or three electrical prongs without substantial design changes or manufacturing set up changes.
Still another object of the present invention to provide a profile rotatable plug which is economical and simple to manufacture.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.